Method and device for purifying hydrogen by coupling a membrane separation method with a pressure swing adsorption cycle

Abstract

The application discloses a method and device for purifying hydrogen by coupling membrane separation and pressure swing adsorption, wherein synthetic gas is compressed in a pressure swing adsorption tower, and first purified hydrogen is obtained by performing first membrane separation; a separation layer composed of two layers of zeolite and two layers of activated carbon in the pressure swing adsorption tower, the first purified hydrogen passes through the separation layer, hydrogen on the permeation side is collected by vacuum adsorption, and desorption gas on the enrichment side is transferred to a secondary separation membrane; hydrogen separation is completed by pressurizing and pushing gas flow at the secondary separation membrane, the obtained hydrogen is pumped to the pressure swing adsorption tower by a vacuum pump for secondary purification, hydrogen on the permeation side is pumped out, and hydrogen on the enrichment side continues to enter the secondary separation membrane as desorption gas for circulation and purification, and the pressure reduction balance in the pressure swing adsorption tower is coupled with the secondary membrane separation cycle, so that pressure reduction and purification are simultaneously performed. The application has the dual characteristics of membrane separation technology and pressure swing adsorption technology, high-purity hydrogen is obtained, the hydrogen yield is improved, the scale of the pressure swing adsorption device is reduced, and the cost is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrogen purification, in particular to a method and device for purifying hydrogen by coupling membrane separation with pressure swing adsorption cycle. BACKGROUND

[0002] The increasing depletion of fossil fuels increases the demand for alternative and clean energy to meet energy demand. Fuel demand is growing rapidly by 0.1 mb / d per year in the late 2020s. Due to the dramatic increase in climate change and air pollution due to the combustion of fossil fuels, alternative energy sources are needed to fully meet the world's energy needs and protect the environment. Hydrogen energy, as a renewable energy source, has become an efficient fuel in the automotive, aerospace and other industries. In order to meet the demand of industrialization, hydrogen needs to be separated and purified. Currently commonly used technologies for purifying and extracting hydrogen include wet washing, dry washing, pressure swing adsorption, membrane separation, and low-temperature distillation. Among them, membrane technology is favored due to its flexible operation, simplicity, energy saving, compactness, small footprint, environmental protection, low operating cost, and ease of integration into industrial processes.

[0003] Pressure swing adsorption (PSA) is a new type of gas adsorption separation technology, which has the following advantages: high product purity; it can generally work at room temperature and low pressure, and does not need heating when regenerating the bed, which is energy-saving and economical; the equipment is simple, and the operation and maintenance are simple; continuous cycle operation can be fully automated. Therefore, since this new technology has been introduced, it has attracted the attention of the industrial sector in various countries, and has been developed and researched by many countries, developed rapidly, and become mature. Especially in the process of hydrogen purification, pressure swing adsorption technology is often used. Membrane separation has a broad application prospect in the field of hydrogen separation due to its simple device structure, high conversion efficiency, low investment cost and environmental friendliness. Different components are separated based on the different diffusion speeds of different components in the separation membrane, including metal membranes, organic membranes, inorganic membranes, organic metal framework (MOFs) membranes, etc., among which Pd-based metal membranes are most commonly used. The principle of action is that high-speed gas is recovered on the separation side by pressure, and low-speed gas is concentrated on the raw material enrichment side, so as to achieve separation.

[0004] The hydrogen obtained by the pressure swing adsorption method has high purity, but the adsorption capacity for impurity gas is weak when the hydrogen content is high, and the impurity gas is increased when the hydrogen content is low, and the hydrogen recovery rate in the residual gas is low, and the hydrogen resource is wasted seriously; the membrane separation method is simple in technology and convenient in operation, the types of membrane materials are various, the selectivity range of the membrane materials to gas is wide, and more than 20% of hydrogen in the raw material can be treated, but the membrane material is expensive, the inlet gas needs to be pressurized layer by layer when the multistage membrane separation (more than 1) is used, the energy consumption and material cost are high, the recovery rate is low, and the separation product is difficult to meet the target requirement when the hydrogen volume fraction is low. In view of the advantages and disadvantages of the above two methods, a single hydrogen recovery technology is often difficult to realize the purpose of high efficiency and high standard rate, and two or more recovery technologies can be combined, the impurities and hydrogen are separated for many times through the grading and circulating treatment of the hydrogen purification process, and the high recovery rate of hydrogen separation and purification is realized.

[0005] Therefore, the present application provides a membrane separation coupled pressure swing adsorption to realize the efficient and high-purity production of hydrogen. SUMMARY

[0006] The present application aims at the deficiencies of the prior art, and provides a method and device for recycling and purifying hydrogen by membrane separation coupled pressure swing adsorption.

[0007] The purpose of the present application is realized by the following technical scheme: a method for recycling and purifying hydrogen by membrane separation coupled pressure swing adsorption, comprising the following steps:

[0008] (1) preliminary purification by membrane separation: the synthesis gas is compressed in the pressure swing adsorption tower, and the first membrane separation is carried out by using Pd-Ag membrane to obtain primary purified hydrogen;

[0009] (2) purification by pressure swing adsorption: the pressure swing adsorption tower has four separation layers composed of two layers of zeolite and two layers of activated carbon, the primary purified hydrogen passes through the separation layers, and the secondary purification is carried out under the pressure difference between the two ends of the pressure swing adsorption tower by using the different diffusion rates of gas in the adsorbent; the hydrogen on the permeation side is collected by vacuum adsorption, and the desorption gas on the enrichment side is transferred to the secondary separation membrane; the adsorption of the pressure swing adsorption tower is completed by vacuum pumping on one side of the adsorption tower to reduce the pressure, and the separation gas is purged and pressurized by introducing the primary separation hydrogen;

[0010] (3) secondary membrane separation-pressure swing adsorption cycle separation and purification: the secondary separation membrane is Pd-Al2O3 inorganic membrane, the gas flow is driven by pressurizing at the secondary separation membrane to complete the hydrogen separation, the obtained hydrogen is pumped to the pressure swing adsorption tower for further purification, the hydrogen on the permeation side is pumped out, and the hydrogen on the enrichment side continues to enter the secondary separation membrane as desorption gas for recycling and purification; the pressure reduction and balance in the pressure swing adsorption tower are coupled with the secondary membrane separation cycle to complete the pressure reduction and purification at the same time.

[0011] Further, the hydrogen gas after secondary separation and purification enters the gas storage tank through the gas pipeline.

[0012] Further, in step (1), the residual gas of the first membrane separation is absorbed by the vacuum pump to the secondary separation membrane to enter the circulation purification.

[0013] Further, the residual gas of the first membrane separation is methane and carbon monoxide.

[0014] Further, the pressure swing adsorption tower simultaneously uses three towers to realize adsorption and desorption alternately to ensure the online state of the adsorbent.

[0015] Further, after the residual gas and hydrogen gas in the tower are separated, the first membrane separation outlet program control valve is opened, the hydrogen gas flows into the pressure swing adsorption tower, the low pressure state in the tower is adjusted to normal pressure, and the adsorption function of the pressure swing adsorption tower is restored.

[0016] Further, the residual gas obtained by the secondary membrane separation needs to enter the pressure swing adsorption tower in a low pressure state to cooperate with the primary membrane separation gas for pressure compensation.

[0017] On the other hand, the application also provides a device for purifying hydrogen gas by membrane separation method coupled with pressure swing adsorption, which comprises a pipeline, an inlet, a Pd-Ag membrane separation device, a pressure swing adsorption tower, a Pd-Al2O3 membrane separation device, a vacuum pump, a hydrogen gas storage tank, a program control valve, a hydrogen gas flow control valve, a first membrane separation pure hydrogen route, a first membrane separation residual gas route, and a residual gas circulation purification route.

[0018] The Pd-Ag membrane separation device is in communication with the inlet, the pressure swing adsorption tower, and the Pd-Al2O3 membrane separation device, and a program control valve is arranged at the inlet.

[0019] The pressure swing adsorption tower is connected with the other adsorption towers, the vacuum pump, and the Pd-Al2O3 membrane separation device through the program control valve and the pipeline.

[0020] The Pd-Al2O3 membrane separation device is in communication with the vacuum pump and the pressure swing adsorption tower.

[0021] The hydrogen gas storage tank is in communication with the adsorption tower and the outlet through the pipeline provided with the program control valve.

[0022] A program control valve is arranged on the outlet.

[0023] Compared with the prior art, the present application has the following advantages and beneficial effects: the present application has the dual characteristics of membrane separation technology and pressure swing adsorption technology, raw gas is pre-processed and then enters a pressure swing adsorption tower for pressure swing adsorption, the treatment capacity can be large, and high-purity hydrogen can be obtained. A hydrogen separation membrane is installed on the backflow pipe of the pressure swing adsorption tower, and a hydrogen storage tank is arranged on the permeation side of the separation membrane. The permeation hydrogen in the hydrogen storage tank is replenished into the pressure swing adsorption tower which has been evacuated by the pressure swing adsorption unit. In this way, high-purity hydrogen is obtained, which not only improves the hydrogen yield, but also reduces the size of the pressure swing adsorption device, thereby reducing the cost. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 It is a schematic diagram of the membrane separation coupled pressure swing adsorption hydrogen separation and purification system.

[0026] Figure 2 It is a schematic diagram of the separation layer in the pressure swing adsorption tower.

[0027] The main elements and processes shown in the figure are: gas inlet, 1, Pd-Ag membrane separation device, 2, pressure swing adsorption tower, 3, Pd-Al2O3 membrane separation device, 4, vacuum pump, 5, hydrogen storage tank, 6, program-controlled valve, 7, hydrogen flow control valve, 8, first membrane separation pure hydrogen route, 9, first membrane separation residual gas route, 10, residual gas circulation purification route, 11, high-purity hydrogen recovery and storage route, 12, zeolite adsorption layer, 13, activated carbon adsorption layer. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below in conjunction with the embodiments, but the embodiments of the present application are not limited to this embodiment;

[0029] As shown in the figure, the method for membrane separation coupled pressure swing adsorption circulation purification of hydrogen of the present embodiment comprises the following steps: Figure 1

[0030] (1) Membrane separation preliminary purification: the synthesis gas is compressed at 6 MPa in the adsorption tower, and the first Pd-Ag membrane separation device is used for high-purity hydrogen separation, to obtain primary purified hydrogen. The metal Ag is used to reduce the hydrogen embrittlement and toxicity of the palladium metal, to improve the permeation rate and separation efficiency of hydrogen in the Pd / metal substrate membrane, and to reduce the permeability of other gases. The residual gas is adsorbed by the vacuum pump to the second Pd-Al2O3 membrane separation device. ​

[0031] (2) Pressure swing adsorption purification: The pressure swing adsorption tower contains four separation layers, such as zeolite-zeolite-activated carbon-activated carbon, as shown in the figure. The purified hydrogen is adsorbed in the adsorption tower, and the secondary purification is performed by using the different diffusion rates of the gas in the adsorbent under the pressure difference between the two ends of the pressure swing adsorption tower. The high-purity hydrogen gas on the permeation side is collected by vacuum adsorption, and the desorption gas on the enrichment side is transferred to the Pd-Al2O3 membrane for secondary separation. Figure 2

[0032] (3) Secondary membrane separation-pressure swing adsorption cycle separation and purification: In the second Pd-Al2O3 membrane separation device, the gas flow is driven by pressure, and the hydrogen separation is completed. The obtained hydrogen is pumped to the pressure swing adsorption tower for purification. The high-concentration hydrogen on the permeation side is extracted, and the enrichment side continues to enter the Pd-Al2O3 membrane as desorption gas for cyclic purification. In the pressure swing adsorption purification process, the high-purity hydrogen obtained by separation and purification in the separation tower is introduced into the gas storage tank through the pipeline.

[0033] In the pressure swing adsorption purification process, the residual gas such as methane and carbon monoxide obtained after the first membrane separation and pressure swing adsorption separation is desorbed by pressure reduction and pumped to the Pd-Al2O3 secondary membrane separation device by a vacuum pump.

[0034] In the pressure swing adsorption purification process, the pressure reduction process is achieved by pumping the gas in the adsorption tower to a low pressure state by a vacuum pump; the pressure increase is achieved by supplementing the high-purity hydrogen after the first membrane separation into the pressure swing adsorption tower to increase the pressure in the tower to normal.

[0035] In the pressure swing adsorption tower, after the separation of the residual gas and hydrogen, the high-purity hydrogen after the first membrane separation is introduced to supplement the pressure and restore the adsorption function of the pressure swing adsorption tower.

[0036] In the pressure swing adsorption purification process, the pressure reduction balance is achieved by entering the secondary membrane separation-adsorption tower route in other adsorption towers and pipelines, and the pressure increase balance process is achieved by entering the hydrogen obtained after the first membrane separation.

[0037] In the pressure swing adsorption tower, the thickness of the activated carbon in the four layers of zeolite-zeolite-activated carbon-activated carbon is 80 cm, and the thickness of the zeolite is 50 cm. The thickness of the zeolite is less than that of the activated carbon.

[0038] In the secondary membrane separation-pressure swing adsorption cycle separation and purification process, the residual gas obtained by the secondary membrane separation needs to enter the low-pressure vacuum adsorption tower to supplement the pressure with the first membrane separation gas.

[0039] ​In the membrane separation coupled pressure swing adsorption hydrogen separation and purification process, the adsorption separation is carried out in the pressure swing adsorption tower, and the adsorption-equilibrium-sweeping-equilibrium are carried out. Specifically, after adsorption by pressure change, pure hydrogen is obtained by 4 layers of zeolite-activated carbon 3 times of adsorption, and then rapidly enters the remaining 1 or 2 pressure swing adsorption towers to realize pressure balance by reducing the pressure of the adsorption tower. The hydrogen flow in the gas storage tank is flowed into the pipeline to complete the gas sweeping and then enters the pressure swing adsorption device again to realize pressure balance by opening the program-controlled valve to enter the 1 or 2 times of membrane separation gas to realize pressure balance. When pressure balance is carried out, the first membrane separator is used to obtain hydrogen to carry out pressure balance, the hydrogen storage tank is closed, the inlet valve is closed, the gas flows through the second membrane separation and the 4 layers of adsorption layers in the pressure swing adsorption tower, and the gas pressure is balanced at the same time to preliminarily separate the impurities and hydrogen.

[0040] As shown in Figure 1 The membrane separation coupled pressure swing adsorption cycle hydrogen purification device of the embodiment, including pipeline, gas inlet, Pd-Ag membrane separation device 1, pressure swing adsorption tower 2, Pd-Al2O3 membrane separation device 3, vacuum pump 4, hydrogen storage tank 5, program-controlled valve 6, hydrogen flow control valve 7, first membrane separation pure hydrogen route 8, first membrane separation residual gas route 9, second membrane separation cycle purification route 10, high-purity hydrogen recovery and storage route 11.

[0041] As shown in Figure 2 The membrane separation coupled pressure swing adsorption cycle hydrogen purification device of the embodiment, the adsorption layers in the pressure swing adsorption tower from top to bottom include 2 layers of zeolite adsorption layers 12 and 2 layers of activated carbon adsorption layers 13.

[0042] The Pd-Ag membrane separation device 1 of the embodiment is in communication with the gas inlet, the pressure swing adsorption tower 2 and the Pd-Al2O3 membrane separation device 3, and the program-controlled valve 6 is arranged at the gas inlet.

[0043] The three pressure swing adsorption towers 2 of the embodiment are connected through the program-controlled valve and the pipeline, and all the pressure swing adsorption towers 2 are connected with the vacuum pump 4 and the Pd-Al2O3 membrane separation device 3.

[0044] The adsorption layers in the pressure swing adsorption tower 2 of the embodiment include the zeolite adsorption layers 12 and the activated carbon adsorption layers 13, and the order is zeolite-zeolite-activated carbon-activated carbon, but is not limited thereto.

[0045] The Pd-Al2O3 membrane separation device 3 of the embodiment is in communication with the vacuum pump 4 and the pressure swing adsorption tower 2.

[0046] The hydrogen storage tank 5 of the embodiment is in communication with the adsorption tower 2 through the pipeline provided with the program-controlled valve 6, and is in communication with the gas outlet through the hydrogen flow control valve.

[0047] The program-controlled valve 6 is arranged on the gas outlet of the embodiment.

[0048] The working principle of the embodiment is as follows: first, the hydrogen mixture gas enters from the gas inlet pipe, enters the Pd-Ag membrane separator 1 for separation, and high-purity hydrogen gas and first membrane separation residual gas are obtained; the high-purity hydrogen gas enters the pressure swing adsorption tower 2 through the gas outlet pipe, and the first membrane separation residual gas enters the Pd-Al2O3 membrane separator 3 through the gas outlet pipe; the high-purity hydrogen gas is subjected to adsorption separation in the pressure swing adsorption tower 2, and is subjected to adsorption of impurity gas through 2 layers of zeolite adsorption layer 12 and active carbon adsorption layer 13 in turn; the specific process is as follows: first, the vacuum pump 4 and the gas outlet valve of the pressure swing adsorption tower 2 are opened, and secondary separation is realized by using the pressure difference and the adsorbent in the tower, and secondary purified hydrogen gas is obtained; the gas outlet valve of the pressure swing adsorption tower is closed, and the pressure stabilizing valve is opened to desorb the residual gas in the adsorption tower 2; then the residual gas enters the Pd-Al2O3 membrane separation device 3 through the gas inlet pipe; the pressure of the enrichment side is increased by introducing the hydrogen gas in the hydrogen gas storage tank 5 into Al2O3, and high-purity hydrogen gas is obtained by realizing separation and purification of hydrogen gas under the Pd membrane through the pressure difference; the hydrogen gas separated by the first membrane, the purified hydrogen gas separated by the pressure swing adsorption tower and the hydrogen gas separated by the second membrane are introduced into the hydrogen gas storage tank 5 through the pipeline; other residual gas is introduced into the Pd-Al2O3 membrane separation device 3 in the pressure swing adsorption tower 2 for separation and purification; the adsorption separation is carried out in the pressure swing adsorption tower 2, and the adsorption-balance-sweep-balance is carried out; specifically, after adsorption by pressure change, pure hydrogen is obtained by 3 times of adsorption through 4 layers of zeolite-active carbon, and then the pure hydrogen is rapidly introduced into the remaining 1 or 2 pressure swing adsorption towers 2 to realize pressure balance of the adsorption tower; the hydrogen gas in the hydrogen gas storage tank 5 flows into the pipeline to complete gas sweeping and is introduced into the pressure swing adsorption tower 2 again, and then is introduced into the 1 or 2 times of membrane separation gas through the opening of the program-controlled valve 6 to realize pressure balance by pressure increase; when the pressure balance is carried out, the hydrogen gas obtained by using the first Pd-Ag membrane separation device 1 is used to balance the pressure, the hydrogen gas storage tank 5 is closed, the gas inlet valve 6 is closed, the gas flows through the second Pd-Al2O3 membrane separation device 3 and the 4 layers of adsorption layers in the pressure swing adsorption tower 2, the gas pressure is balanced, and the impurities and hydrogen gas are preliminarily separated.

[0049] The above embodiment is used to explain and illustrate the present application, but is not used to limit the present application, and any modification and change made to the present application within the spirit and protection scope of the claims of the present application falls within the protection scope of the present application.

Claims

1. A method for purifying hydrogen by a membrane separation process coupled with a pressure swing adsorption cycle, characterized in that, The method comprises the following steps: (1) preliminary purification by membrane separation: the synthesis gas is compressed in a pressure swing adsorption tower, and a first membrane separation is performed using a Pd-Ag membrane to obtain first purified hydrogen; (2) purification by pressure swing adsorption: the pressure swing adsorption tower has four layers of separation layers composed of two layers of zeolite and two layers of activated carbon, the first purified hydrogen passes through the separation layers, and under the pressure difference at both ends of the pressure swing adsorption tower, secondary purification is performed by using the different diffusion rates of the gas in the adsorbent, the hydrogen on the permeation side is collected by vacuum adsorption, and the desorption gas on the enrichment side is transferred to the secondary separation membrane; the adsorption of the pressure swing adsorption tower is completed by vacuum pumping of the adsorption tower on one side to reduce the pressure, and the separation gas is purged and pressurized by introducing the first separation hydrogen; (3) secondary membrane separation-pressure swing adsorption cycle separation and purification: the secondary separation membrane is a Pd-Al2O3 inorganic membrane, and the gas flow is driven by pressurization at the secondary separation membrane to complete hydrogen separation, the obtained hydrogen is pumped to the pressure swing adsorption tower for further purification, the hydrogen on the permeation side is pumped out, and the hydrogen on the enrichment side continues to enter the secondary separation membrane as desorption gas for cyclic purification, the pressure reduction balance in the pressure swing adsorption tower is coupled with the secondary membrane separation cycle, and the pressure reduction and purification are performed simultaneously; after the remaining gas and hydrogen in the tower are separated, the first membrane separation outlet program control valve is opened to allow the hydrogen to flow into the pressure swing adsorption tower, the low pressure state in the tower is adjusted to return to normal pressure, and the adsorption function of the pressure swing adsorption tower is restored.

2. The method of claim 1, wherein the method is characterized by: The hydrogen purified by the secondary separation is introduced into a gas storage tank through a gas pipeline.

3. The method of claim 1, wherein the method is characterized by: In step (1), the remaining gas of the first membrane separation is adsorbed by a vacuum pump to the secondary separation membrane for cyclic purification.

4. The method of claim 3, wherein the method further comprises: purifying the hydrogen gas using a pressure swing adsorption cycle. The remaining gas of the first membrane separation is methane and carbon monoxide.

5. The method of claim 1, wherein the method further comprises: purifying the hydrogen gas using a pressure swing adsorption cycle. The pressure swing adsorption tower simultaneously uses three towers to realize adsorption and desorption alternately to ensure the online state of the adsorbent.

6. The method of claim 1, wherein the method further comprises: purifying the hydrogen gas using a pressure swing adsorption cycle. The remaining gas obtained by the secondary membrane separation needs to enter the pressure swing adsorption tower in a low pressure state to cooperate with the first membrane separation gas for pressure compensation.

7. An apparatus for purifying hydrogen by a membrane separation process coupled with a pressure swing adsorption cycle according to the method of any one of claims 1 to 6, characterized in that, The device comprises a pipeline, an air inlet, a Pd-Ag membrane separation device (1), a pressure swing adsorption tower (2), a Pd-Al2O3 membrane separation device (3), a vacuum pump (4), a hydrogen storage tank (5), a program control valve (6), a hydrogen flow control valve (7), a first membrane separation purified hydrogen route (8), a first membrane separation remaining gas route (9), and a remaining gas cyclic purification route (10); The Pd-Ag membrane separation device (1) is in communication with the air inlet, the pressure swing adsorption tower (2), and the Pd-Al2O3 membrane separation device (3), and a program control valve (6) is arranged at the air inlet; The pressure swing adsorption tower (2) is connected to the other adsorption towers (2), the vacuum pump (4), and the Pd-Al2O3 membrane separation device (3) through program control valves and pipelines; The Pd-Al2O3 membrane separation device (3) is in communication with the vacuum pump (4) and the pressure swing adsorption tower (2); The hydrogen storage tank (5) is in communication with the adsorption tower (2) and the gas outlet through a pipeline provided with a program control valve (6); A program control valve (6) is arranged on the gas outlet.

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